Comments

Hardware timestamping for Intel 82580 didn't work in either 2.6.36 or 2.6.37. Comparing it to Intel's igb-2.4.12 I found that the timecounter_init clock/counter initialization was done too early.
Anders Berggren
Halon Security
lab-slang-1:~# diff -u linux-2.6.37/drivers/net/igb/igb_main.c linux/drivers/net/igb/igb_main.c
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On Thu, 2011-02-03 at 02:39 -0800, Anders Berggren wrote:
> Hardware timestamping for Intel 82580 didn't work in either 2.6.36 or 2.6.37. Comparing it to Intel's igb-2.4.12 I found that the timecounter_init clock/counter initialization was done too early. > > Anders Berggren> Halon Security
Thanks Anders, I will add this patch to my queue of igb patches.

On Feb 4, 2011, at 12:23 AM, Jeff Kirsher wrote:
> Thanks Anders, I will add this patch to my queue of igb patches.
Another question which I asked John Ronciak earlier; is there any work on TX timestamping for IPv6? In 2.6.37 sock_tx_timestamp() is only called in IPv4 UDP (net/ipv4/udp.c) and raw sockets (net/packet/af_packet.c).
Would it be meaningful if I tried to add it to ipv6/ip6_output.c as Marcus D. Leech suggested in http://kerneltrap.org/mailarchive/linux-netdev/2009/11/10/6260604 and http://kerneltrap.org/mailarchive/linux-netdev/2009/11/11/6260643 --
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> -----Original Message-----> From: Anders Berggren [mailto:anders@halon.se]> Sent: Tuesday, February 08, 2011 7:25 AM> To: Kirsher, Jeffrey T> Cc: Ronciak, John; e1000-devel@lists.sourceforge.net;> netdev@vger.kernel.org> Subject: Re: [E1000-devel] [PATCH] fixing hw timestamping in igb> > On Feb 4, 2011, at 12:23 AM, Jeff Kirsher wrote:> > > Thanks Anders, I will add this patch to my queue of igb patches.> > Another question which I asked John Ronciak earlier; is there any work> on TX timestamping for IPv6? In 2.6.37 sock_tx_timestamp() is only> called in IPv4 UDP (net/ipv4/udp.c) and raw sockets> (net/packet/af_packet.c).> > Would it be meaningful if I tried to add it to ipv6/ip6_output.c as> Marcus D. Leech suggested in http://kerneltrap.org/mailarchive/linux-> netdev/2009/11/10/6260604 and http://kerneltrap.org/mailarchive/linux-> netdev/2009/11/11/6260643
Anders,
The question of IPv6 support for TX timestamping is still under discussion. We are trying to understand the use case for it as well as how it would be used. We have had no customers asking for this type of support (at least not yet). If there is kernel work going on regarding it then maybe this needs to be looked at closer.
Other than being a science project, what is your use case for the TX timestamping in IPv6?
Cheers,
John
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On Feb 8, 2011, at 5:27 PM, Ronciak, John wrote:
> The question of IPv6 support for TX timestamping is still under discussion. We are trying to understand the use case for it as well as how it would be used. We have had no customers asking for this type of support (at least not yet). If there is kernel work going on regarding it then maybe this needs to be looked at closer. Other than being a science project, what is your use case for the TX timestamping in IPv6?
We're developing a "hardware/kernel timestamp ping" for Linux in C. It's part of a complete SLA platform (appliance based on Debian with XMLRPC APIs). It's both a science project (Chalmers University, Gothenburg) and a commercial project (Tele2).
Commercial SLA appliances from Cisco and Juniper typically have a accuracy of XXX microseconds. Our hardware ping, using Intel 82580 NICs, have an accuracy of 8 nanoseconds. That is VERY good.
The reason for supporting IPv6 is, well, because it's the future ;) --
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On Wed, 2011-02-09 at 09:24 +0100, Anders Berggren wrote:
> Our hardware ping, using Intel 82580 NICs,> have an accuracy of 8 nanoseconds.
Perhaps you mean 8 nanosecond resolution?
Is documentation available for this claim?
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On Feb 9, 2011, at 9:56 AM, Joe Perches wrote:
> Perhaps you mean 8 nanosecond resolution?> Is documentation available for this claim?
To clarify; we haven't proven this either mathematically not in a laboratory (looking at actual data transmissions). Also, it's the jitter accuracy we're concerned with. We have simply assumed that the jitter of two independent servers (exchanging timestamps) over a very short cable is an approximation of jitter accuracy.
As you say; if the resolution is 8 ns, the accuracy is of course worse than 8 ns. So far, we have however assumed the accuracy to be within the same order of magnitude.--
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